Method for producing sharp corners in metal stock



G. LAWSON 2,023,638 G S HARP CORNE 5 IN METAL STO mun Patented Dec. 10,1935 UNITED STATES METHOD FOR PRODUCING SHARP CORNERS IN METAL STOCKGust Lawson, Jamestown, N. Y., assignor to Dahlstrom Metallic DoorCompany, Jamestown, N. Y., a corporation .of New York ApplicationFebruary 15, 1932, Serial No. 592,900

6 Claims.

This invention relates to a method for producing sharp corners onangularly bent metal stock.

Metal doors, door enclosures, furniture, etc., are produced from oneform or another of angularly bent stock. The stock is generally formedin a press or roller die. The angular bends produced in this fashion arerounded rather than sharp. Since there are many instances where it isessential that the angular corners be sharp and well defined, it hasbeen necessary to bend the material and produce a slight bulge on theoutside of the bend. This bulge was then removed by belt sanding down tothe angularly disposed flanges of the material to produce a sharp outercorner. While this method gives the desired appearance, it has beenfound that the stock in and adjacent the bend is greatly thinned andweakened, and as a result the material often fractures at this point.This has occurred particularly in metal door and enclosure structureswhere unavoidable vibration occurs.

The present invention discloses a method for producing a sharp and welldefined angular corner with little or no weakening of the stock alongthe bend and without the necessity of performing extra work such assanding or dressing down to obtainv the desired sharpness.

The principal object of the invention lies in the provision of a methodfor producing a sharp corner in metal stock.

Another object of the invention is the method of bending metal stock toproduce a sharp and well defined corner by means of a two-step process.

A further object of the invention lies in the method for producing wellsharply defined corners in metal stock without greatly distorting themetal.

Another and further object of the invention is to provide a method forusing a punch which causes a previously bent piece of stock to fill andconform to the sharp contour of a given die.

Another and still further object of the invention lies in the method ofproducing a sharply defined angular corner in metal stock, the thicknessof the metal at the angle being somewhat greater than the normalthickness of the stock.

Other and further objects of the invention will be more clearlyunderstood from a consideration of the following specification which istaken in conjunction with the accompanying drawings, and in which Fig. 1is a front elevation of a press about to perform the first operation ona piece of fiat metal stock;

Fig. 2 shows a punch projecting into a die and the stock bent to a givenangle;

Fig. 3 is an end view of the stock removed from the press;

Fig. 4 shows a punch and die for the second step of the process with thepunch about to cause the round corner to flow into and fill the diecavity;

Fig. 5 shows the punch engaged with the stock 5 at the completion ofthis operation;

Fig. 6 is an enlarged fragmentary view, showing the punch withdrawn fromengagement with the stock;

Fig. 7 shows a slight modification of the punch and die, the die in thisinstance being arranged with laterally movable jaws, similar to those ofthe punch;

Fig. 8 shows the press engaged with the stock, and the elements of bothpunch and die moved laterally; and

Fig. 9 shows a method of ejection through the released spread of thepunch and die.

Reference is now had to the drawings in which is shown a press,generally indicated by the reference numeral I 0, which includes a punchII and die l2. The punch and die in this showing are arranged to producea right angle corner in a strip of metal stock IS. The punch, mounted inany convenient manner in a head I5, is vertically movable to engage thestock l3 and causes it to be pressed into the V-shaped cavity I6 of thedie. The die is mounted in any convenient manner in a base ll. Inasmuchas the present invention has only to do with a punch and die and theresults obtainable therewith on the stock I 3, further and moreelaborate showing of thesupporting structure is unnecessary.

In Figure 1 of the drawings, the stock I3 is shown mounted on the die l2with the punch II in position preparatory to the first operation. Whenthe punch l l moves downward into the die, as shown in Figure 2, thestock 13 is bent to a right angle. It will be noted when the stock 'I3is thus bent to produce an angle element, the sides 40 I 9 and 20 meetin a right angle 2| which is defined by a sharp inner corner 22 and acurved outer corner 23. Figure 3 of the drawings shows the stock uponremoval from the press 'at the completion of the first operation.

The punch Il may be removed from the head l5 and another punch 25substituted therefore. This punch comprises substantially duplicateelements 26 and 21. The elements are arranged with coinciding transverserecesses 29, forming together a pocket 30 in which a resilient means,such as a rubber block 3!, is located. Above the pocket 30 a spacingstrip 33 is mounted between the adjacent faces of the punch elements 28and 21. A drilled and tapped opening 34 is provided in the element 26and a coinciding opening 35 is made in the element 21, this latteropening receiving a screw 31 which, when engaged with the threads of theopening 34, draws the elements 26 and 21 together, slightly compressingthe block 60 3|. It will be noted that the lower ends of the punchelements are shaped to jointly form a right angle, a gap 38 occurringtherebetween. This gap is for the purpose of permitting the elements 26and 21 of the punch to move toward each other under certain conditionsof operation which will hereinafter be more fully set forth. The lowerends or jaws 39 and 40 of the elements 26 and 21 are formed with sawteeth 4|. The teeth on one element project downwardly and toward theteeth of the other element. The purpose of these teeth is to provideengagement of the punch with the stock l3 during the second operation.The die I2, in this modification, may be the same as that shown for thefirst operation.

After mounting the angularly shaped stock in the die 12, the punch 25 islowered to engagement with the stock. As pressure is exerted upon thepunch, the teeth of the elements 26 and 21- bite into the stock and uponfurther downward pressure of the punch, move toward each othercompressing the block 31. This inward and downward pressure ofthe punchelements causes the stock to fiow downwardly to completely fill theV-shaped cavity of the die I2. A comparison between the showing of thestock in Figures 4 and Sindicates that the downward and inward pressureexerted by the relatively movable punch elements has caused the roundcorner 23 of the angle 22 to change to a sharp corner defined by theshape of the cavity in the die. As soon as downward pressure on thepunch ceases, the resilient block 3i tends to spread-the punch elements26 and 21, causing the teeth 4| thereof to readily release the stock. Itwill be noted that the inner surface of the stock adjacent the anglebears the teeth marks of the punch but since such marring of thestockalways occurs on the inside of the angle and is concealed, such marringis not objectionable. However, since the teeth are merely for grippingthe stock, any other known arrangement may be employed.

Attention is particularly directed to the en, larged fragmentary view ofthe stock in Figure 6. It will be noted that the stock is now thickeracross the angle 2| than it is along the sides l9 and 20. In otherwords, the metal has been made to flow to produce a thick as well assharp corner which will more effectively resist fracture than the cornerformed by the first operation. Itis well to mention that the firstoperation described and shown in Figures 1 and 2 is quite similar topresent methods used in bending stock with the exception that there isusually a slight enlargement in the base of the die cavity which allowsthe metal to flow downwardly to form a bulge of sufficient thickness topermit sanding down to produce a sharp corner. This is common practiseand was referredto in the introductory paragraph. 7

A modification of the structure for completing the second step in theprocess of bending stock to produce sharp outside corners is shown inFigures '1 through 9 of thedrawings. In this instance, a die 43 isprovided with a V-shaped cavity 44 which terminates in a narrow flatbottom wall 45. Mounted in the cavity 44 are duplicate oppositelydisposed shoes 41. The shoes are formed with co-axial pockets 48 inwhich is located spring or other resilient means 49. The purpose of thespring is to normally hold the shoes apart and in engagement with thesloped walls of the die. The upper portion of the shoes are shaped toprovide a cavity 4|, the angularity of which corresponds to thatdescribed in connection with the first step in this process.

The stock I3 is placed in the cavityll and when the punch 25 movesdownwardly, the shoes 41 are likewise moved downwardly and inwardly.This movement of the shoes 41 is simultaneous with the inward 'movementof the elements 28 and 21 of the punch. When the lowermost position ofthe punch is reached, the cavity II assumes a sharply defined angle atits base which is filled by the stock caused to flow through the actionof the elements of both punch and die. This modification is betteradapted for fast work since, upon raising the punch, the elements 28 and21 as well as the shoes 41 of the die spread apart, thus, permittingready removal of the shaped stock.

Attention is directed to the fact that applicant can produce a sharplydefined corner without the aid of the teeth shown on the lower faces ofthe punch elements 26 and 21 and without the aidof relatively movableshoes forming the die. These slight modifications as well as otherdeviations in structure, which may be suggested by the present showing,are contemplated and within the scope of applicants invention in so faras they may be defined in the hereunto annexed claims.

Having thus set forth my invention what I claim as new and for which Idesire protection by Letters Patent is:

1. The method of bending metal stock to produce a sharp outer cornerconsisting in first; bending the stock to the desired shape, and second;applying forces adjacent to and converging at the bend in the stock.

2. The method of bending metal stock to produce sharp outer cornersconsisting in first; bending the stock to partially conform to the shapeof a given die, and second; applying forces to increase the thickness ofthe stock at the bend and fill the die.

3. The method of bending metal stock to produce sharp outer cornersconsisting in first; bending the stock to partially conform to the shapeof a given die, and second; subjecting the inner faces of the stockadjacent the bend to convergent forces to cause the stock at the bend tofill the die.

4. The method of bending metal stock to produce sharp outer cornersconsisting in first; bending the stock to partially conform to the shapeof a given die, and second; applying force by which to crowd additionalmetal into the bend to fill the die.

5. The method of bending metal stock to produce sharp outer cornersconsisting in first; bending the stock to a given shape, second; 10-cating the bent stock in a die of said given shape, and third; applyingconverging forces to the inner walls of the stock adjacent the bend tocause the stock to fill the-die at the bend.

6. The method of bending metal stock to produce sharp outer cornersconsisting in first; bending the stock to a given shape, second;locating the bent stock in a die of said given shape, and third;applying forces to crowd additional metal into the bend and increase thethickness of the stock at this point.

GUST LAWSON.

